Portable battery



FIG. 1 is a perspective view of a portable battery showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines in the drawings are for the purpose of illustrating portions of the portable battery that form no part of the claimed design. 

CLAIM The ornamental design for a portable battery, as shown and described. 